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Expanded memory is an umbrella term for several incompatible technology variants. The most widely used variant was the Expanded Memory Specification (EMS), which was developed jointly by Lotus Software, Intel, and Microsoft, so that this specification was sometimes referred to as "LIM EMS". LIM EMS had three versions: 3.0, 3.2, and 4.0.
Extended memory is located above 1 MB, includes the high memory area, and ends at 16 MB on the Intel 286 and at 4 GB on the Intel 386DX and later.. In DOS memory management, extended memory refers to memory above the first megabyte (2 20 bytes) of address space in an IBM PC or compatible with an 80286 or later processor.
CEMM, for Compaq Expanded Memory Manager was the first so-called PC "memory manager" for Intel 80386 CPUs, able to provide expanded memory (EMS) emulation by using the virtual memory features and the virtual 8086 mode of the CPU. It was present in Compaq DOS 3.10, shipping with the Compaq Deskpro 386 in September 1986. [1] [2]
Expanded memory managers such as Quarterdeck's QEMM product and Microsoft's EMM386 supported the expanded memory standard without requirement for special memory boards. On 386 and subsequent processors, memory managers like QEMM might move the bulk of the code for a driver or TSR into extended memory and replace it with a small fingerhold that ...
EMM386 is the expanded memory manager of Microsoft's MS-DOS, IBM's PC DOS, Digital Research's DR-DOS, and Datalight's ROM-DOS [1] which is used to create expanded memory using extended memory on Intel 80386 CPUs. There also is an EMM386.EXE available in FreeDOS. [2]
Expanded memory in the IBM PC. In 1985, the companies Lotus and Intel introduced Expanded Memory Specification (EMS) 3.0 for use in IBM PC compatible computers running MS-DOS. Microsoft joined for versions 3.2 in 1986 and 4.0 in 1987 and the specification became known as Lotus-Intel-Microsoft EMS or LIM EMS.
Hardware extensions allowed access to more memory than the 8086 CPU could address through paging memory. This memory was known as expanded memory. An industry de facto standard was developed by the LIM consortium, composed of Lotus, Intel and Microsoft. This standard was the Expanded Memory Specification (EMS). Pages of memory from expanded ...
In DOS memory management, the upper memory area (UMA) is the memory between the addresses of 640 KB and 1024 KB (0xA0000–0xFFFFF) in an IBM PC or compatible. IBM reserved the uppermost 384 KB of the 8088 CPU 's 1024 KB address space for BIOS ROM , Video BIOS , Option ROMs , video RAM, RAM on peripherals, memory-mapped I/O , and obsoleted ROM ...